1. Field of the Invention
The present invention relates to a position measuring system and/or a navigation system, and more particularly to a system using a GPS. The present invention also relates to a navigation method, an information service method, an automotive vehicle, and audio information transmitting and receiving method.
2. Description of the Related Art
Conventionally, a navigation system utilizing a position measuring system using artificial satellites called a GPS (Global Positioning System) has been widely known and has already been in widespread use in vehicles. In addition, a so-called hybrid type navigation system for navigation based on information from a gyro sensor or the like have also been used extensively in tunnels, valleys between tall buildings in town, and so on, where GPS radio waves from a satellite do not reach. A variety of receivers have been developed for position measuring systems using the GPS for applications other than in vehicles.
However, while a conventional system demonstrates its performance to some extent when it can receive a GPS radio wave, it has a disadvantage in that data from a gyro sensor, generated at a place where a GPS radio wave does not reach, include so many cumulative errors that they are not worth using. Also, while map matching is frequently performed, this is a mere correction of data so absolute measuring accuracy cannot be improved thereby. If the matching leads to an erroneous road, a worse result is introduced than without matching.
In addition, even when a GPS radio wave can be received, it cannot straightforwardly be said that a sufficient accuracy can be always provided since there is a mode for intentionally degrading the accuracy by the administrator of the GPS (the Department of Defence of the United States), and since radio wave transmission conditions may be disturbed by a perturbed ionospheric layer or the like which deteriorates the measuring accuracy.
The present invention is intended to solve the foregoing problems and provides for absolute position measuring without: relying only on GPS radio waves to achieve high performance at a low cost.
According to a first aspect of the present invention, a position measuring apparatus includes a first position measuring means for position measuring a first position by receiving a first radio wave, a second position measuring means for position measuring a second position by receiving a second radio wave, an evaluating means for evaluating uncertainty in data derived from the first position measuring means and/or the second position measuring means, and a selecting means for selecting data from the first position measuring means or the second position measuring means based on an output signal from the evaluating means.
According to a second aspect of the present invention, a navigation apparatus includes a first position measuring means for position-measuring a first position by receiving a radio wave from a GPS satellite, a second position measuring means for measuring a second position by receiving a radio wave from a base station of a cellar telephone system without transmitting any request signal for position-measuring to the base station, an evaluating means for evaluating uncertainty of in data derived from the first position measuring means and/or the second position measuring means, a selecting means for selecting data from the first position measuring means or the second position measuring means based on an output signal from the evaluating means, a data storage means for storing map data, a display signal generating means for generating a display signal by combining an output signal from the selecting means and output data from the data storage means, and a display means for displaying the display signal.
According to a third aspect of the present invention, a position measuring method includes a first position measuring step for position measuring a first position by receiving a first radio wave, a second position measuring step for position measuring a second position by receiving a second radio wave, an evaluating step for evaluating uncertainty in data derived from the first position measuring step and/or the second position measuring step, and a selecting step for selecting data from the first position measuring step or the second position measuring step based on an output signal of the evaluating step.
According to a fourth aspect of the present invention, a navigation method includes a first position measuring step for position measuring a first position by receiving a radio wave from a GPS satellite, a second position measuring step for position measuring a second position by receiving a radio wave from a base station of a cellular telephone system without transmitting any request signal for position measuring to the base station, an evaluating step for evaluating uncertainty in data derived from the first position measuring step and/or the second position measuring step, a selecting step for selecting data from the first position measuring step or the second position measuring step based on an output signal from the evaluating step, and a display step for displaying a combined signal of an output signal from the selecting step and map data.
According to a fifth aspect of the present invention, an information distribution method includes a request signal receiving step for receiving a service request signal from a user, a transmitting step for transmitting music related information from a base station of a mobile telephone network in a predetermined cell of the service request signal, and an audio signal generating step for generating an audio signal from the music related information at a subscriber""s side.
According to a sixth aspect of the present invention, a car apparatus includes a first position measuring means for position measuring a first position by receiving a radio wave from a GPS satellite, a second position measuring means for position measuring a second position by receiving a radio wave from a base station of a cellar telephone system without transmitting any request signal for position measuring to the base station, an evaluating means for evaluating uncertainty in data derived from the first position measuring means and/or the second position measuring means, a selecting means for selecting data from the first position measuring means or the second position measuring means based on an output signal from the evaluating means, a data storage means for storing map data, a display signal generating means for generating a display signal by combining an output signal from the selecting means and an output data from the data storage means, and a display means for displaying the display signal.
According to a seventh aspect of the present invention, an audio signal transmitting method for transmitting an audio signal with a first priority and an audio signal with an n-th priority (n is an integer equal to or greater than 2.) includes a transmitting step for transmitting the audio signal in a predetermined order with a priority corresponding to the priority of the audio signal to be transmitted.